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# Protocol Buffers - Google's data interchange format
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# Copyright 2008 Google Inc.
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# http://code.google.com/p/protobuf/
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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# http://www.apache.org/licenses/LICENSE-2.0
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""Class for decoding protocol buffer primitives.
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Contains the logic for decoding every logical protocol field type
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from one of the 5 physical wire types.
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__author__ = 'robinson@google.com (Will Robinson)'
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from google.protobuf import message
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from google.protobuf.internal import input_stream
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from google.protobuf.internal import wire_format
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# Note that much of this code is ported from //net/proto/ProtocolBuffer, and
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# that the interface is strongly inspired by WireFormat from the C++ proto2
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class Decoder(object):
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"""Decodes logical protocol buffer fields from the wire."""
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def __init__(self, s):
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"""Initializes the decoder to read from s.
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s: An immutable sequence of bytes, which must be accessible
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via the Python buffer() primitive (i.e., buffer(s)).
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self._stream = input_stream.InputStream(s)
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def EndOfStream(self):
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"""Returns true iff we've reached the end of the bytes we're reading."""
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return self._stream.EndOfStream()
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"""Returns the 0-indexed position in |s|."""
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return self._stream.Position()
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def ReadFieldNumberAndWireType(self):
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"""Reads a tag from the wire. Returns a (field_number, wire_type) pair."""
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tag_and_type = self.ReadUInt32()
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return wire_format.UnpackTag(tag_and_type)
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def SkipBytes(self, bytes):
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"""Skips the specified number of bytes on the wire."""
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self._stream.SkipBytes(bytes)
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# Note that the Read*() methods below are not exactly symmetrical with the
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# corresponding Encoder.Append*() methods. Those Encoder methods first
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# encode a tag, but the Read*() methods below assume that the tag has already
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# been read, and that the client wishes to read a field of the specified type
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# starting at the current position.
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"""Reads and returns a signed, varint-encoded, 32-bit integer."""
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return self._stream.ReadVarint32()
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"""Reads and returns a signed, varint-encoded, 64-bit integer."""
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return self._stream.ReadVarint64()
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"""Reads and returns an signed, varint-encoded, 32-bit integer."""
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return self._stream.ReadVarUInt32()
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"""Reads and returns an signed, varint-encoded,64-bit integer."""
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return self._stream.ReadVarUInt64()
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"""Reads and returns a signed, zigzag-encoded, varint-encoded,
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return wire_format.ZigZagDecode(self._stream.ReadVarUInt32())
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"""Reads and returns a signed, zigzag-encoded, varint-encoded,
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return wire_format.ZigZagDecode(self._stream.ReadVarUInt64())
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def ReadFixed32(self):
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"""Reads and returns an unsigned, fixed-width, 32-bit integer."""
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return self._stream.ReadLittleEndian32()
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def ReadFixed64(self):
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"""Reads and returns an unsigned, fixed-width, 64-bit integer."""
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return self._stream.ReadLittleEndian64()
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def ReadSFixed32(self):
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"""Reads and returns a signed, fixed-width, 32-bit integer."""
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value = self._stream.ReadLittleEndian32()
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if value >= (1 << 31):
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def ReadSFixed64(self):
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"""Reads and returns a signed, fixed-width, 64-bit integer."""
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value = self._stream.ReadLittleEndian64()
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if value >= (1 << 63):
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"""Reads and returns a 4-byte floating-point number."""
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serialized = self._stream.ReadString(4)
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return struct.unpack('f', serialized)[0]
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def ReadDouble(self):
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"""Reads and returns an 8-byte floating-point number."""
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serialized = self._stream.ReadString(8)
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return struct.unpack('d', serialized)[0]
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"""Reads and returns a bool."""
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i = self._stream.ReadVarUInt32()
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"""Reads and returns an enum value."""
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return self._stream.ReadVarUInt32()
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def ReadString(self):
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"""Reads and returns a length-delimited string."""
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length = self._stream.ReadVarUInt32()
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return self._stream.ReadString(length)
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"""Reads and returns a length-delimited byte sequence."""
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return self.ReadString()
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def ReadMessageInto(self, msg):
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"""Calls msg.MergeFromString() to merge
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length-delimited serialized message data into |msg|.
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REQUIRES: The decoder must be positioned at the serialized "length"
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prefix to a length-delmiited serialized message.
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POSTCONDITION: The decoder is positioned just after the
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serialized message, and we have merged those serialized
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length = self._stream.ReadVarUInt32()
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sub_buffer = self._stream.GetSubBuffer(length)
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num_bytes_used = msg.MergeFromString(sub_buffer)
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if num_bytes_used != length:
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raise message.DecodeError(
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'Submessage told to deserialize from %d-byte encoding, '
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'but used only %d bytes' % (length, num_bytes_used))
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self._stream.SkipBytes(num_bytes_used)
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def ReadGroupInto(self, expected_field_number, group):
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"""Calls group.MergeFromString() to merge
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END_GROUP-delimited serialized message data into |group|.
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We'll raise an exception if we don't find an END_GROUP
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tag immediately after the serialized message contents.
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REQUIRES: The decoder is positioned just after the START_GROUP
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POSTCONDITION: The decoder is positioned just after the
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END_GROUP tag for this group, and we have merged
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the contents of the group into |group|.
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sub_buffer = self._stream.GetSubBuffer() # No a priori length limit.
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num_bytes_used = group.MergeFromString(sub_buffer)
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if num_bytes_used < 0:
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raise message.DecodeError('Group message reported negative bytes read.')
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self._stream.SkipBytes(num_bytes_used)
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field_number, field_type = self.ReadFieldNumberAndWireType()
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if field_type != wire_format.WIRETYPE_END_GROUP:
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raise message.DecodeError('Group message did not end with an END_GROUP.')
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if field_number != expected_field_number:
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raise message.DecodeError('END_GROUP tag had field '
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'number %d, was expecting field number %d' % (
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field_number, expected_field_number))
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# We're now positioned just after the END_GROUP tag. Perfect.
added
removed
python/google/protobuf/internal/decoder.py
